Method of treating foodstuffs



Jan. 24, 1950 P.- L. SPENCER 2,495,429

METHOD OF TREATING FOODSTUFFS Filed Oct. s, 1945 MAGNET/FUN OSCILLH TOR F000 T0 BE Oil.

SYSTEM OSC/L L0 70/? /M//Vr0/ fmay Z. 6/01 0541 Patented Jan. 24, 1950 METHOD OF TREATING FOODSTUFFS Percy L. Spencer, West Newton, Mass, assignor to Raytheon Manufacturing Company, Newton, Mass, a corporation of Delaware Application October 8, 1945, Serial No. 620.919

6 Claims. (Cl. 99-217) My present invention relates to the treatment of foodstuffs, and more particularly to the cooking thereof through the use of electromagnetic energy.

Such energy has been used before for this purpose, but the frequencies employed have been relatively low, for example, not over 50 megacycles. I have found that at frequencies of this order of magnitude, the energy necessarily ex pended in order to generate suiiicient heat to satisfactorily cook the foodstuff is much too high to permit the practical use of the process. I have further found, however, that this disadvantage may be eliminated by employing wave lengths falling in the microwave region of the electromagnetic spectrum, for example, wave lengths of the order of 10 centimeters or less. By so doing, the wave length of the energy becomes comparable to the average dimension of the foodstuff to be cooked, and as a result, the heat generated in the foodstuff becomes intense, the energy expended becomes a minimum, and the entire process becomes eflicient and commercially feasible.

It is, therefore, one of the objects of my present invention to provide an eflicient method of employing electromagnetic energy for the cooking of foodstufis.

In the accompanying specification I shall describe, and in the annexed drawing shOW, an illustrative embodiment of the method and means for treating foodstuff of my present invention. It is, however, to be clearly understood that I do not wish to be limited to the details herein shown and described for purposes of illustration only, inasmuch as changes therein may be made without the exercise of invention and within the true spirit and scope of the claims hereto appended.

In said drawing, the single figure is a schematic arrangement of apparatus which may be utilized to carry out the method of my present invention.

Referring now more in detail to the aforesaid illustrative embodiment of my present invention, with particular reference to the drawing illustrating the same, the numerals l and H generally designate electron-discharge devices of the magnetron type, each including, for example, an

evacuated envelope l2, made of highly conductive material, such as copper, and provided with a plurality of inwardly-directed, radially-disposed anode vanes l3. The arrangement is such that each pair of adjacent anode vanes l3 forms,

together with that portion of the envelope l2 7 lying therebetween, a cavity .resonator whose natural resonant frequency is, as is well known to those skilled in the art, a function of the geometry of the physical elements making up the same. For the purposes of my present invention it is desirable that the dimensions of each such cavity resonator be such that the wave length of the electrical oscillations adapted to be generated therein is comparable to the average dimension of the foodstufi' to be cooked, for example, of the order of 10 centimeters or less.

Centrally located in each envelope I 2 is a highly electro-n-emissive cathode member M, for example, of the well-known alkaline-earth metal oxide type, said cathode member being provided with conventional means (not shown) for raising the temperature thereof to a level suflicient for thermionic emission.

Each electron-discharge device It! is completed by magnetic means (not shown) for establishing a magnetic field in a direction transversely of the electron path between the cathode and anode members thereof.

The conductive envelopes l2 of the electrondischarge devices l0 and II are connected, respectively, by conductors l5 and Hi, to the opposite terminals of the secondary winding ll of a transformer I 8, the primary winding I! of said transformer being connected to a source of raw A.-C., for example, the conventional cycle power lines. The cathodes H of said electron-discharge devices I0 and H are tied together by conductors 20 and 2|, which are, in turn, connected, by a conductor 22, to a center tap on the secondary winding I 'l of the transformer I8.

Thus, the electron-discharge devices I0 and II are connected for push-pull operation, whereby said devices alternately deliver hyper-frequency energy to a common, hollow wave guide 23 through coaxial transmission lines 24 and 25 which are coupled to their respective oscillators, for example, by loops 26 and 21.

Adjacent the outlet end of the wave guide 23 I provide an appropriate, transversely-moving conveyor system 28 for carrying the foodstuff to be cooked into a region where it will be exposed to the energy emanating from said wave guide, the speed at which said conveyor system is operated being determined by the nature of the particular foodstuff to be cooked, and the time required for cooking the same.

With the system described, I have found thatan egg may be rendered hardboiled with the expenditure of 2 kw.-sec. This compares with an expenditure of 36 kw.-sec. to conventionally cook the same. I have also found that with my system a potato requires the expenditure of about 240 kw.-sec., which compares with 72,000 kw.-sec. necessary to bake the same in an electric oven. These examples are, it is to be clearly understood, merely illustrative. I have observed similar results with other foodstuffs. In each instance, where the wave length of the energy is of the order of the average dimension of the foodstuff to be cooked, the process is very efficient, requiring the expenditure of a minimum amount of energy for a minimum amount of time.

This completes the description of the aforesaid illustrative embodiment of my present invention. It will be noted from all of the foregoing that my process is simple and easily practiced; it is economical; and it requires relatively simple and inexpensive equipment.

Other objects and advantages of my present invention will readily occur to those skilled in the art to which the same relates.

What is claimed is:

1. In the method of treating foodstuffs, those steps which include: generating electromagnetic wave energy of a wavelength falling in the microwave region of the electromagnetic spectrum; concentrating and guiding said wave energy within a restricted region of space and exposing the foodstuff to be treated to the energy so generated for a period of time sufficient to cook the same to a predetermined degree.

2. In the method of treating foodstuffs, those steps which include: generating electromagnetic wave energy of a wavelength falling in the microwave region of the electromagnetic spectrum; concentratin and guiding said energy within a restricted region of space; and conveying the foodstuff to .be treated through said region of space at such a rate of speed as to expose the same to said energy for an interval of time sufficient to cook the same to a predetermined degree.

3. In the method of treating foodstuffs, those steps which include: generating electromagnetic wave energy of a wavelength falling in the microwave region of the electromagnetic spectrum;

concentrating and guiding said energy within a restricted region of space to establish an electromagnetic field therein; exposing the foodstuff to be treated to said field for a period of time sufficient to cook the same to a predetermined degree; and moving said foodstuff relative to said field while said foodstuff is so exposed.

4. In the method of treatin foodstuffs, those steps which include: generating electromagnetic wave energy of a wave length of substantially ten centimeters; concentrating and guiding said wave energy within a restricted region of space and exposing the foodstuff to be treated to the energy so generated for a period of time sufficient to cook the same to a predetermined degree.

5. In the method of treating foodstuffs, those steps which include: generatin electromagnetic wave energy of a wave length of substantially ten centimeters; concentrating and guiding said energy within a restricted region of space; and conveying the foodstuff to be treated through said region of space at such a rate of speed as to expose the same to said energy for an interval of time sufficient to cook the same to a predetermined degree.

6. In the method of treating foodstuffs, those steps which include: generating electromagnetic wave energy of a wave length of substantially ten centimeters; concentrating and guiding said energy within a restricted region of space to establish an electromagnetic field therein; exposing the foodstuff to be treated to said field for a period of time sufficient to cook the same to a predetermined degree; and moving said foodstuff relative to said field while said foodstuff is so exposed.

PERCY L. SPENCER.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 1,181,219 Goucher May 2, 1916 1,863,222 Hoermann June 14, 1932 1,900,573 McArthur Mar. 7, 1933 1,945,867 Rawls Feb. 6, 1934 1,981,583 Craig Nov. 20, 1934 1,992,515 Uhlmann Feb. 26, 1935 2,052,919 Brogdon Sept. 1, 1936 2,094,602 Kassner Oct. 5, 1937 2,382,033 Supplee et a1 Aug. 14, 1945 

1. IN THE METHOD OF TREATING FOODSTUFFS, THOSE STEPS WHICH INCLUDE: GENERATING ELECTROMAGNETIC WAVE ENERGY OF A WAVELENGTH FALLING IN THE MICROWAVE REGION OF THE ELECTROMAGNETIC SPECTRUM; CONCENTRATING AND GUIDING SAID WAVE ENERGY WITHIN A RESTRICTED REGION OF SPACE AND EXPOSING THE FOODSTUFFS TO BE TREATED TO THE ENERGY SO GENERATED FOR A PERIOD OF TIME SUFFICIENT TO COOK THE SAME TO A PREDETERMINED DEGREE. 